Experimental realization of ultrathin graphene nanosheets opened up a new horizon for the academic and applied research. Even though graphene exhibits numerous unusual physical properties and applications thereof, its semi-metallic nature disables graphene to be used in optical/electronic applications. Semi-conducting inorganic analogues of graphite-like transition metal dichalcogenides (TMDs) are one of the most attractive alternatives for such applications. Molybdenum disulfide (MoS2) is well studied and shows an interesting layered structure as well as unusual physical properties. Reports such as Applied Physics Letters 2013,102 (12), demonstrate that MoS2-based electronic devices out-perform graphene-based ones. Nano Lett. 2011, (11 (12), 5111-5116) describes that the bulk MoS2 has an indirect bang gap of 1.2 eV and does not show photoluminescence properties; whereas electronic properties of monolayered MoS2 change drastically resulting in a direct band gap semi-conductor with a band gap of 1.9 eV. When the ultra-thin MoS2 nanosheets are confined to zero-dimension (0D), the quantum size effects, and the edge effects become very significant. However, the synthesis and characterization of MoS2 nanoclusters is still in its infancy. Previously reported methods are very tedious and/or yield polydisperse distribution of particles. Existing techniques to yield high quality thin layer MoS2 nanosheets or nanoparticles include solvent exfoliation and mechanical exfoliation. However, both these techniques fail in the large-scale exfoliation of TMDs.
Since graphene as well as MoS2 layers are held together by common force called van der Waals forces, exfoliation techniques adopted for graphene can be easily extrapolated for MoS2 as well. Coleman and co-workers have established the exfoliation of graphite and MoS2 using solvent exfoliation methods in organic solvents in Nat. Nanotech. 2008, 3 (9), 563-568 and Science 2011, 331 (6017), 568-571. However, in their approach, only a few layered sheets of graphene and MoS2 have been obtained. As already known, extraction of materials from solvent exfoliation route is very difficult for any practical application. Hence, it is important to develop new methods to synthesize dichalcogenide quantum dots having formula MX2 with single or few layers in a simple, cost-effective, environment-friendly manner. Further, direct deposition of these nanoparticles onto conducting substrates could lead to enhanced electronic conductivity.